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KMID : 1101320050370010056
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Korean Journal of Clinical Laboratory Science
2005 Volume.37 No. 1 p.56 ~ p.60
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Evaluation of Gestational Age Median Value by Use of the Quad Test with Dimeric Inhibin A for Korea Pregnant Women
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Yoo Ja-Young
Choi Sam-Kyu
Cho Young-Suk
Hwang Do-Young
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Abstract
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Human chorionic gonadotrophin (hCG) and unconjugated estriol (uE3) were added to AFP to make what is commonly known as the Triple test. The Triple test combines results from these three tests and has been a standard screening procedure for several years. Recent studies have demonstrated the usefulness of adding inhibin-A to Down's syndrome risk assessment. The Quad test adds dimeric Inhibin-A (DIA) to the three other markers and uses the same computer program to calculate risk factors. Testing was performed between 14 and 21 weeks of gestation. Sample size were 648 samples and period of study was from 1, July, 2004 to 30, September, 2004. Used analytical methods for AFP, hCG and uE3 were radioimmunoassay (RIA) and dimeric inhibin A was enzyme-linked immunosorbent assay (ELISA). Adding dimeric inhibin-A as a fourth marker to the standard triple test increases the detection rate from 62 % to 75 % with a false-positive rate of 5%. The DIA based Quad test has been shown to be the most effective second trimester screening test for Down's syndrome suitable for routine use. Increased DIA values are observed during normal pregnancy where a bimodal pattern response is seen. Values increase during the first trimester, decline after 14 weeks, and re-ascend between 17-25 weeks. Values for DIA may be additionally elevated during a Down's syndrome pregnancy. Dimeric inhibin A is a glycoprotein hormone made by the ovary and placenta. DIA levels are twice as high in Down‘s syndrome pregnancies. AFP, hCG, and uE3 levels vary with gestational age, and incorrect gestational dating will influence results. DIA levels do not vary substantially with gestational age, resulting in greater screening accuracy. Although the Quad test is an improvement over the Triple test, it is important to underscore the fact that a positive test on both should be done. Most women who initially screen positive will be found to be carrying normal babies when amniocentesis and definitive diagnostic chromosome analysis are done.
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KEYWORD
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Quad test, Inhibin-A, Triple test, Down's syndrome
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